In recent years, superheated steam processing apparatuses that use superheated steam to wash, dry, and sterilize processing objects have been devised.
It will be noted that, regarding steam, latent heat necessary for a state change from water at boiling point to steam at boiling point is the largest, and for example, referring to superheated steam at 700° C., the ratio between a heat quantity necessary to change water at 60° C. into saturated steam at 130° C. and a heat quantity necessary to change saturated steam at 130° C. into superheated steam at 700° C. is approximately 2:1. That is, disposing of steam after use leads to a large calorific loss, and therefore recycling of used steam is desirable.
Apparatuses adapted to recycle superheated steam include, as disclosed in Patent Literature 1, a heat treatment device that is configured to, on the basis of the temperature inside a heat treatment chamber, control the temperature and supply a quantity of superheated steam supplied from a superheating device to the heat treatment chamber, and control a returning flow rate of the superheated steam returned to a steam inlet side of the superheating device.
However, the heat treatment device described above controls the returning flow rate of the superheated steam returned to the steam inlet side of the superheating device, on the basis of the temperature inside the heat treatment chamber. Accordingly, part of the used steam having passed through the heat treatment chamber is discharged, and therefore the heat treatment device does not fundamentally solve the calorific loss problem.